A centrifugal pump of that type is described, for example, in European patent EP-0 207 430-B1. In one embodiment which is illustrated, in particular, in FIG. 13 of that document, the coupling formation of the rotor is constituted by a curved region of resilient material, the radially outermost surface of which has toothing. This region of resilient material is inserted axially into an annular cavity in the rotor, the radially outermost surface of which is provided with corresponding toothing. This solution requires an accurate construction of the resilient region and of the corresponding toothing of the rotor. The insertion of the resilient region into the rotor requires fairly precise relative angular positioning in order to prevent interference during insertion. In addition, the resilient region is not constrained in a stable manner on the rotor, in particular in the axial direction.
In an alternative solution described in European patent EP-0 287 984-B1, a quantity of viscous fluid, such as an oil or a grease having lubricating properties, is placed and sealed in the cavity of the impeller hub and is intended to damp the impact between the coupling formations of the impeller and of the rotor and to muffle the noise correspondingly generated. This solution is difficult to put into practice and presents problems from the point of view of maintaining the sealed isolation of the viscous fluid in the cavity of the impeller.